Galaxies

Stars are clustered together in enormous groups called galaxies.The galaxies were created as stars forming from spinning clouds of condensing gas were pulled towards each other by gravity.Some galaxies still rotate rapidly maintaining a spiral shape while others slow down and form ellipses or less regular shapes.Large galaxies may have 1000 billion stars but even the smaller contains a few hundred thousand.

There are four types of galaxy:

Elliptical :The most common type of galaxy,ellipticals contain mostly old stars and vary in shape from ball to egglike.

Spiral: These disc-shaped galaxies are flat with a central nucleus of old stars.New stars form from clouds of gas in the spiral arms.

Barred Spiral: In a third of spiral galaxies the nucleus is elongated into a bar.The vast spiral arms extend from the end of the bar.

Irregular: The rarest galaxies are those that do not fit any known pattern.Some have a hint of a spiral or elliptical structure.

Galaxy facts:

The brightest ,oldest and most distant of galaxies are quasi-stellar objects or quasars some of which are 14 billion light years away.

Some astronomers think that the Milky Way is a barred spiral galaxy.

The Milky Way

The Sun is just one of 500,000 million stars in our galaxy,the Milky Way.Ours is a spiral galaxy with a nucleus of old stars surrounded by a halo of even older stars.All the young stars such as the Sun are located in the spiral arms.The galaxy is called the Milky Way because it looks like a bright creamy band of stars stretching through space when viewed from earth.